Ideas
I've done a small handful of experiments (Version 1.120.117.1030 DX11 (most recent)) because I wanted to test if my mods were causing the issue. Here is what I did:
I removed my mods folder, deactivated mods in the game just to be safe, deleted the localthumbcache.package file and repaired the game. I opened up the savefile that has the issue and created a new savefile. Without mods, the older savefile still had the issue, the new savefile didn't. With all my mods added back to the game (one by one), nothing changed - the new savefile still didn't have the issue. I deactivated mods again and the error popped up in the new savefile. I activated mods again, the new savefile still has the issue, even after repairing the game. Maybe switching mods on and off repeatedly is one root of the issue? The game automatically disables mods after every update, so everyone toggles the switch at least after every update. I couldn't link it to my mods themselves though, since the new savefile worked completely fine with all mods enabled - the error occurred first after disabling mods. (I restarted the game after every change of course.)
Another time (in another savefile), the bug was caused by Direct X11 and switching to Direct X9 fixed it. Switching to DX9 doesn't fix the bug in the old savefile I used in this experiment, so that's not the (only) root issue for this savefile.
I hope this has helped. How can I send my savefile(s) for further investigation?